1. Field of the Invention
The present invention is directed toward the field of search and retrieval systems, and more particularly to a knowledge based multi-document search and retrieval system.
2. Art Background
In general, search and retrieval systems permit a user to locate specific information from a repository of documents, such as articles, books, periodicals, etc. For example, a search and retrieval system may be utilized to locate specific medical journals from a large database that consists of a medical library. Typically, to locate the desired information, a user enters a "search string" or "search query." The search query consists of one or more words, or terms, composed by the user. In response to the query, some prior art search and retrieval systems match words of the search query to words in the repository of information to locate information. Additionally, boolean prior art search and retrieval systems permit a user to specify a logic function to connect the search terms, such as "stocks AND bonds", or "stocks OR bonds."
In response to a query, a word match based search and retrieval system parses the repository of information to locate a match by comparing the words of the query to words of documents in the repository. If there is an exact word match between the query and words of one or more documents, then the search and retrieval system identifies those documents. These types of prior art search and retrieval systems are thus extremely sensitive to the words selected for the query.
The terminology used in a query reflects each individual user's view of the topic for which information is sought. Thus, different users may select different query terms to search for the same information. For example, to locate information about financial securities, a first user may compose the query "stocks and bonds", and a second user may compose the query "equity and debt." For these two different queries, a word match based search and retrieval system would identify two different sets of documents (i.e., the first query would return all documents that have the words stocks and bonds and the second query would return all documents that contain the words equity and debt). Although both of these query terms seek to locate the same information, with a word search and retrieval system, different terms in the query generate different responses. Thus, the contents of the query, and subsequently the response from word based search and retrieval systems, is highly dependent upon how the user expresses the query term. Consequently, it is desirable to construct a search and retrieval system that is not highly dependent upon the exact words chosen for the query, but that generates a similar response for different queries that have similar meanings.
Prior art search and retrieval systems do not draw inferences about the true content of the document. If the search and retrieval system merely compares words in a document with words in a query, then the content of a document is not really being compared with the subject matter identified by the query term. For example, a restaurant review article may include words such as food quality, food presentation, service, etc., without expressly using the word restaurant because the topic, restaurant, may be inferred from the context of the article (e.g., the restaurant review article appeared in the dining section of a newspaper or travel magazine). For this example, a word comparison between a query term "restaurant" and the restaurant review article may not generate a match. Thus, although the main topic of the restaurant review article is "restaurant", the article would not be identified. Accordingly, it is desirable to infer topics from documents in a search and retrieval system in order to truly compare the content of documents with a query term.